Use of Absolute Weights and Mass Coefficients of Beagle Dog Internal Organs Relative to Body and Brain Weights in Preclinical Studies

Introduction . Toxicity of new drugs should be evaluated in two species of laboratory animals, one of them being nonrodent species. In preclinical studies, dogs are used as second laboratory animal species. In toxicological research, analysis of organ weights is an important parameter to detect the target organs in test animals. Data on organ absolute and relative weights in animals aged 8–16 months are available in the existing scientific publications, however, none of these papers provide calculations relative to the weight of brain. The analysis of organ weights relative to the weight of brain is useful when changes in the normal dynamics of body weight are observed, since weight of a brain is more stable than weight of a body. Therefore, the objective of the present research is to determine absolute weights and reference intervals of mass coefficients of beagle dog organs relative to body and brain weights, and to compare the mass coefficients of dog organs, which have been calculated as a proportion of organ to body weight, to the data available in the literature. Materials and Methods . The study was conducted at the “Home of Pharmacy” (Leningrad Region) in 2022. To calculate the reference intervals, the data on 25 males and 17 females aged 14–22 months that participated in control groups of various experiments were used. The electronic scales were used to record organ weights. The statistical outliers were not evaluated, since the number of animals was small. A nonparametric method was chosen for calculating intervals. To create the reference intervals, the absolute organ weights and coefficients calculated relative to body and brain weights were analysed. For further visual comparison of data retrieved by the authors to that available in the literature, the mean value and standard deviation were calculated in the Statistica 10 software. Results . Absolute weights and reference intervals of mass coefficients of the heart, lungs with trachea, thymus, liver, spleen, kidneys, adrenal glands, brain, testes and ovaries were established relative to body and brain weights of beagle dogs aged 14 to 22 months. When compared to the data available in literature, discrepancies in liver weights of females were revealed, which may be caused by the different degree of organ exsanguination during necropsy. On the whole, the values obtained for the organs coincided with that in the publications, with the exception of thymus: since the dogs in the present research were older than animals described in the literature, the obtained discrepancy confirms the age-related involution of thymus. Discussion and Conclusion . Availability of internal laboratory reference intervals enables correct interpretation of the obtained results of organ weight measurements, thus, prevents the false positive and false negative results. Further research in this area will reduce data scattering, which in turn will enhance the quality, reliability and reproducibility of scientific results. Moreover, in the future, this may result in reduction of the number of animals used in experiments.